In order to keep the speed of an aircraft in such a speed range, it is known to provide the aircraft with a protection system configured to limit the angle of attack and attitude of the aircraft, in order to avoid reaching the stall speed of the aircraft, and to gradually introduce, from a threshold speed, a pull up depth command in order to avoid reaching the structural limit of the aircraft.
Nevertheless, these solutions do not make it possible to protect the aircraft against loss of maneuverability. In particular, at low speeds, the capacity of the aircraft to pull up decreases until it is canceled out. Under such conditions, the pilot no longer has a sufficient maneuvering margin in terms of angle of attack to increase the load factor of the aircraft and quickly modify the trajectory of the aircraft.
Likewise, at high speeds, the capacity of the aircraft to dive decreases until it is canceled out, altering the pilot's maneuvering margin to modify the trajectory of the aircraft.
To resolve this problem, it has been proposed to equip the aircraft with a speed control system, activated once the speed of the aircraft crosses a predetermined threshold, and configured to enslave the speed of the aircraft by controlling the throttle.
This solution is not fully satisfactory. Indeed, this solution is based on controlling only the thrust, irrespective of the flight configuration of the aircraft, without intervening on the drag of the aircraft, and is therefore generally not optimal. Furthermore, the implementation of the protection, which involves going from manual control of the throttle to automatic control of the throttle, can disrupt the manual piloting of the aircraft by the pilot.
Also known from document FR 2,958,033 is a device for displaying information relative to a flight configuration of an aircraft, comprising information relative to an energy variation of the aircraft and an energy variation range that can be achieved by said aircraft. This energy variation range depends on the thrust values that can be generated by the engines of the aircraft and the drag force exerted on the aircraft depending on the position of the air brakes.
Such a device does not provide the pilot with information relative to the possibility of exceeding speed limits in light of the current acceleration of the aircraft.